Disquiet over new spying laws is "opposition for the sake of politics", Prime Minister John Key says.

The Government yesterday secured a one-vote majority to pass the controversial Government Communications Security Bureau amendment bill. UnitedFuture leader Peter Dunne agreed to back the legislation after a series of changes.

The legal fix-it is required after a loophole, which allowed the foreign intelligence agency to illegally spy on more than 80 Kiwis, was exposed.

The proposed law will sanction surveillance of New Zealand residents on behalf of the police, Defence Force and Security Intelligence Service.

Labour and the Greens refuse to vote for the bill without an independent inquiry into the security services.

Labour proposed a sunset clause, which would have allowed the GCSB to resume its work on behalf of law enforcement agencies, while the review was undertaken.

Key has dismissed an inquiry as unwarranted.

He said today that opposition by both parties is "just for the sheer sake of politics".

Labour passed legislation governing the GCSB in 2003 which was "far weaker ... had poor oversight and a poorly defined set of rules," he argued.

"It's not opposition because the bill doesn't work or won't improve the current structure," he said.

The legislation is "significantly strengthened" from its initial draft, he said.

"It's actually a good piece of legislation. I think it balances the rights and needs between national security and privacy of New Zealanders.

"There is significant oversight. It is a far better piece of legislation than was previously the case back in 2003."

Key said yesterday he was open to discussions with other parties to increase support for the bill.

"Quite a lot of legislation passes by one vote. In the end, it's a majority," he said today.

He wants the bill back before Parliament for debate "reasonably soon".

Under the changes secured by Dunne, the SIS and GCSB will be subject to review in 2015, and every five to seven years. The GCSB will also be required to reveal the number of warrants granted every year and come before public hearings on its financial performance.

The Government will also have to seek approval from Parliament to expand the number of agencies GCSB can assist.

A public meeting to protest against the law, and the Telecommunications (Interception Capability & Security) Bill, will take place in Auckland on Thursday.